Focus Problem

chicodawg · December 19, 2006

I posted a "people" photo taken with my new Canon 70-200mm f/2.8L lens. There was/is an issue with focus. I don't know if it's my camera (me) shaking or DOF or I'm using the wrong focus point on the subject. I'm having inconsistent results with this and my 20D. Of course, it can't be the camera, so what can I work on?

At f/2.8, the DOF is this narrow (see below)? The feathers closest to the camera are sharp(er), IMHO, but the head is completely OOF. :dunno

IMG128a.jpg

@ 200mm, f/2.8, 1/4000, ISO 100 - other than cropped, no modification.

Harryb · December 19, 2006

I'm thinking that its the DOF in that shoot. Your shutter speed was 1/4000 sec so you had lots of room to step down your aperture setting for that shot. If it had been shake then teh feathers would not have been as sharp.

Thusie · December 19, 2006

Good morning,

Gonna wade in here since I like shooting wide open a lot:D

Where you using the center point only? This would be super impotant with super shallow DOF, center point focus should be just below the eye of the bird. That said everything but the head will be OOF at close range, the farther you are away from the subject the larger your DOF. There is a site that you can plug in the numbers..(anyone have that handy?) for your lens an camera, rather fun.

The focus looks good at the focus point and like Harry said you had tons of shutter speed to stop down which would have gotten the whole bird. I shoot with the 200 f2.8 prime at anywhere from f2.8-f3.5 and the focus point becomes mission critical, one twitch and you can loose it at close range. Grand fun tho'.

Congrats on a wonderful lens!!!

Harryb · December 19, 2006

Thusie brings up a good point. If your software can show you the focus point I think it will show that it was on the bird's shoulder. If you are going to use a wide open aperture setting you should focus on the eye of the subject.

pathfinder · December 19, 2006

That looks about right for DOF at 200mm at f2.8 fairly close in to the front element - ie: not focused at infinity. At least that is what I expect with my 70-200 at f2.8

If you want the eye sharp with a telephoto lens, you MUST get an AF point on the eye if you hope to have a sharp eye at f2.8, not much DOF to be found there with a 200mm lens. This gets even more important at 400 or 600mm

wxwax · December 19, 2006

Looks like a classic case of shallow depth of field.

If you want that effect, set your camera's autofocus point to one that's near the head, or better yet the eye, of the bird.

Otherwise, stop down.

It's a good lesson in thinking about aperature size and depth of field before each shot. No, I'm not being condescending. Been there, done that too many times myself!

chicodawg · December 20, 2006

Thanks for all the responses. I am experimenting (learning) more and more. I knew DOF would be shallow at 2.8, but not THAT shallow! It's a small bird!

This is a new lens to me. My other zoom is a f/4.5-5.6. Having 2.8 is great, but some getting used to.

Thanks again!

Seefutlung · December 20, 2006

Remember that your focus is a flat plane of variable thickness dependant upon your aperature. Shooting/angling up at the bird will change the focus plane to an angle parallel to the front element. So in this case your shallow DOF is slicing through the bird at an angle. You may have had sufficient DOF at 2.8 for sharp wing feathers and sharp head had the bird been plumb to your eye ... but (the big but) the angle of shooting actually increased the distance between your DOF plane and the bird's head.

Gary

chicodawg · December 20, 2006

Thanks Gary, another valuable lesson I will have to remember.

This gull and I were on the 5th Floor of The Pier in St. Petersburg, FL. So nothing but blue was behind it. It was standing on the railing.

Might have been easier to adjust the aperature to get the whole bird in focus.

Well, it's virtually free to experiment with it some more, so I'll probably do that soon. Hehe

Thanks again!
Mike

Focus Problem

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